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Date November 2018 Marks available 2 Reference code 18N.3.HL.TZ0.1
Level Higher level Paper Paper 3 Time zone TZ0 / no time zone
Command term Explain Question number 1 Adapted from N/A

Question

Measurements of the lung capacity of a student were recorded using a spirometer and displayed with a data logger. Initially the student was at rest, then changed to carrying out strenuous exercise. The results are displayed in the graph.

Calculate the ventilation rate at rest, giving the units.

[1]
a.

Explain the changes in ventilation after 35 seconds.

[2]
b.

Suggest how the total lung volume at rest would differ for a patient with emphysema.

[1]
c.

Outline the function of pneumocytes in the lungs.

[2]
d.

Markscheme

12 breaths per minute/6 litres per minute ✔

 

Accept answers from 11 to 12 breaths per minute.

Accept answers from 5.5 to 6 litres per minute.

Answer must include breaths or litres and a standard unit of time.

Correct:
eg: 12 breaths / minute
eg: 0.1 L sec–1 or 6 L min–1

Incorrect:
eg: but 12 breaths = 0 marks

a.

a. the volume of air per breath increases
OR
the volume of each breath reaches a maximum/levels off
OR
frequency of ventilation/breaths per minute increases ✔

b. exercise increases «rate of cellular» respiration/energy use/blood CO2/acidity ✔

c. exercise causes increased demand for oxygen/removal of carbon dioxide ✔

d. maximum rate/depth of ventilation is determined by the capacity of the student ✔

b.

«total resting lung volume» would be greater ✔

c.

a. type I pneumocytes carry out gas exchange ✔ 
OWTTE

b. type II pneumocytes secrete surfactant/fluid OWTTE
OR
type II pneumocytes create a moist surface inside the alveoli
OR
type II pneumocytes reduce surface tension between alveoli
OR
type II pneumocytes prevent the sides of the alveolus adhering to each other ✔

d.

Examiners report

[N/A]
a.
[N/A]
b.
[N/A]
c.
[N/A]
d.

Syllabus sections

Core » Topic 6: Human physiology » 6.4 Gas exchange
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